A satellite image shows Hurricane Sandy. Hurricane Sandy, which pounded the Bahamas early today as it careened toward the eastern United StatesAFP/Getty Images

The prelude to Frankenstorm – a tropical system combining with a mid-fall nor’easter and forecast to amass over New Jersey late this weekend – will begin with light rain falling over most of the state starting Saturday, forecasters with the National Weather Service say.

But by Monday morning, Sandy roiling off the Atlantic coast is expected to encounter a low-pressure system heading southeast across the United States, and create a potentially damaging hybrid of heavy rains and sustained and powerful winds.

Although the National Hurricane Center said that “some weakening” of the hurricane is possible in the next 24 hours or so as it moves northeast, Sandy, or its tropical storm offshoot, is still expected to run into a weather system developing northwest.

Although that front is now forecast to stall across central Pennsylvania, the fusion of that cooler system with tropical-force winds and rain, along with Monday’s full-moon tides, creates the potential for devastating floods to soak the state, particularly along the coast, although a relatively dry summer could mitigate damage, forecasters say.

"It borders on rare to unprecedented on its potential,” the state climatologist at Rutgers University, David Robinson, said on Thursday afternoon.

On its own, Sandy is expected to bring strong and sustained winds and dump several inches of rain when the brunt of the storm hits the state.

Local government agencies throughout the state are cautioning residents to prepare for possible power outages, in some cases lasting days.

HURRICANE SANDY UPDATE

STATUS: Sandy was a Category 1 hurricane as of 11 a.m. Friday

STRENGTH: Maximum sustained winds of 80 mph; 970 mb pressure

LOCATION: Sandy was 25 miles north-northeast of Great Abaco Island and 460 miles south-southeast of Charleston S.C. as of 11 a.m.

SPEED & DIRECTION: Moving north at 6 mph Friday morning, down from 10 miles per hour earlier in the day

Essex County Sheriff Armando Fontoura said he was holding conference calls with PSE&G, the National Weather Service, State Police and others to manage preparations and any needed responses.

Fontoura, who is also the jurisdiction's emergency management coordinator, said that since Hurricane Irene last year, the county had bolstered its rolling stock in preparation for a similar weather event.

“We’ll be prepared and ready to roll,” he said. “We’ll be around all weekend long.”

He said that county personnel across county departments were being given assignments and that the emergency management office was keeping the county’s 22 municipalities abreast of groundwork.

“We’re preparing for the worst and praying for the best – not hoping, praying,” Fontoura said.

Forecasters expect it to remain a category 1 for at least the next few days, although its wind field is expected to grow in size.

The storm, moving northwest at 10 mph, is slowing down even further as it veers north tonight and then northeast on Saturday, according to the Hurricane Center.

Tropical storm conditions are possible for the Carolina coast Saturday night, the National Weather Service says.

At least 21 people have so far been killed by storm-related damage, including 11 in Cuba, as howling winds and rain toppled houses and ripped off roofs. Sandy also killed one person while crossing Jamaica on Wednesday and 10 in Haiti, where heavy rains from the storm's outer bands caused flooding in the impoverished and deforested country.

As of 8 a.m., Sandy is churning hurricane-force winds of 80 mph extending 35 miles from the storm’s center, which is near the northwestern Bahamas, about 200 miles west of West Palm Beach, Fla., according to the hurricane center. Tropical-storm-force winds are reaching nearly 300 miles from the storm’s center, the center says.

The Associated Press and Star-Ledger staff writer Stephen Stirling contributed to this story.